the reader to a total of some fifteen texts that I deem to be of key importance in illuminating the cultural logic that runs through North Korean society

As she explains:

I analyze and interpret the rituals and language embodied in North Korean literature, concentrating mainly on works published during the 1970s and 1980s

Given the paucity of first-hand information about North Korea, this certainly seems like a worthwhile approach.
Ryang, born and raised in Japan in a community of Koreans closely linked to North Korea -- many of whom were (voluntarily) repatriated to North Korea -- and having visited the country herself (albeit most recently in 1985), is particularly well-positioned to undertake such a study.
(She was also able to rely on her father's large haul of North Korean books, invaluable primary source material.)
Ryang's interest is, first and foremost (and as the subtitle suggests), ethnological, but her extensive reliance on -- and both quotation from and summary of -- literary texts makes her work of additional value to those readers (such as myself) whose interest is predominantly literary.
In fact, Ryang quotes and summarizes at great -- often page-long -- length, and one of the frustrations of the text is that it shows so tantalizingly much while the stories and (quoted/summarized) books themselves remain incomplete and inaccessible.
Ryang emphasizes the social/cultural/political significance of the figure of Kim Il Sung -- the longtime leader of the nation, and the ultimate father/founder-figure.
Ryang diagnoses a shift in North Korean society in the 1970s and 1980s, as: "Kim Il Sung was transformed from a theoretico-ideological leader into an ethico-spiritual one" -- i.e. the notion became one of: "Kim Il Sung the sovereign and sacred".
The figure thus also stands in contrast to his son and successor, Kim Jong Il, a replaceable leader-figure of a different order than the near-godhead Kim Il Sung.
(Ryang was able to include mention of Kim Jong Il's passing in late 2011, and briefly discusses then-likely (and now actual) successor Kim Jong Un, but is understandably (if unfortunately) not able to integrate this closely with the rest of the book; given her focus on the shift in attitudes in the 1970s and 1980s this is hardly fatal -- but it would be interesting to see how she reads these more recent changes as well.)
It is fascinating to learn how often Kim Il Sung appeared in works of fiction -- thus also giving them a documentary quality, as well as helping to shape the image of the 'Great Leader'.
Significantly, for a long time he is a portrayed as a very human figure -- almost saintly in his benevolence and wisdom, and his deep affection for his flock and country, but still distinctly human -- while Ryang reports that: "in literature published since the 1990s, Kim Il Sung leaves the human world and appears as a bundle of virtues".
(Recall that Kim Il Sung only died in 1994.)
As Ryang shows, many -- arguably nearly all -- aspects of North Korean society have been heavily influenced by the Kim Il Sung-figure, and his position as venerated over-lord
In her examples from and analysis of various texts Ryang shows how both purely domestic issues are handled, as well as North Korean perspectives on foreign influence and might, including the continued role of America as much-hated enemy.
Some of the examples are fascinating, from the particularly creepy story about Kim Il Sung making a detour to the local toy factory to suggest they really should make guns that fire real (toy) bullets, so the kindergarten kids can truly enjoy their game of: "catching and shooting migungnom" ('American bastards'), to the extended look at the immensely popular film (and film script) 'Unsung Heroes'.
(Stretching her definition of form here, Ryang here relies of Lin Jin-U's 1981 film script but decides it: "will henceforth be referenced as a novel for the sake of simplicity".)
Ryang divides her book into three main sections, discussing 'Love', 'War', and 'Self', and she offers considerable insight into how North Korean society 'works', as well as what lies behind this.
Not surprisingly, the orientation in each case is largely to the 'Great Leader', the embodiment of the collective and of the greater good; nevertheless, Ryang shows that there is still a significant role for the individual, and the possibility of self-realization -- albeit always in relation to the Great Leader-figure.
So, too, self-criticism is seen as an important quality.
Reading North Korea does enhance our picture of North Korean society -- though it is better at suggesting how it evolved from the time of the Korean War through the 1980s than more recent times.
To those of us particularly interested in the fiction available to North Korean readers the book offers tantalizing glimpses, but also much frustration: it's difficult to judge how significant individual stories and books were, or even how large a readership they had (only with regards to the film version of 'Unsung Heroes' does Ryang give any idea of how large an audience any of these works reached).
And, of course, Ryang only offers glimpses of the works themselves, in summarizing them or quoting from them: this gives a decent sense of them, but isn't a substitute for the works themselves.
(Given that there is still essentially no North Korean fiction available in English this is particularly frustrating -- though, of course, hardly Ryang's fault (and her objective here is an entirely different one).)
Reading North Korea is a useful complement to the still very limited literature about North Korea, and particularly helpful in showing the role of the figure of Kim Il Sung (and how this has shifted over the decades).
Ryang's approach is fairly effective -- though the balance between summary/quotation and exegesis can be difficult to strike -- and her arguments quite convincing, and it is certainly invaluable in presenting a clearer picture of the North Korea of the 1970s and 1980s.
Too bad she doesn't examine more -- and more contemporary -- fiction.